Reclaiming of rubber



A Patented Feb. 17, 1942 2,273,506 RECLAIMING F" RUBBER Otto 'Biichle,Cologne, Germany, assignor, by

mesne assignments, to General Aniline & Film Corporation, New York, N.Y., a corporation of Delaware NoDrawing. Application April l'l, 1939,Serial No. 268,331. In Germany April 28,1936

. 3 Claims.

The present invention relates to improvements in the reclaiming ofrubber from vulcanized products. In practice, natural rubber isreclaimed from its vulcanizates, for instance, by

heating the same with a relatively high con centrated caustic sodasolution or with the solutlon of amineral acid. Moreover, the heatnigcan be enected in the presence or an indifferent high boiling solventsucn as tetrahydronapnthaiene.- 'l'hese processes generally require theappllcation 01' high temperatures of about 160 L1 facilitating acomplete interpenetration of the bile heating being continued for aprolonged time,

say about 0 to 15 hours.- Whereas processes 01 the character describedare practically used for the reclaiming of natural rubber from itsvulcanizates, there is still alack of suitable reclaiming processes forsynthetic rubber-like materials which are obtained by the polymerizationor butadienes -or co-polymerization of butadienes and otherpolymerizable compounds. i It is the object of the present invention todevelop a new process which allows one to efiect the reclaiming ofrubber from its vulcanizates at a lower temperature and more quicklythan it was hitherto possible. Another object of my invention resides inthe developing of auxiliary agents which are suitable for the reclaimingor natural rubber as well as of synthetic rubberlike materials of thecharacter described. Other objects will be apparent from the followingdescription and claims;

I have found that the reclaiming of rubber (either natural or synthetic)by heating in the presence of oxygen (for instance in form of air) ifdesired in the presence of asolvent, can be considerably accelerated, ifthe reclaiming process is performed in the presence of a small amount ofa mono-aryl hydrazine. In general, about 1-5% of the said auxiliaryagents are sufficient to bring about the desired result, though loweramounts, i. e. down to about 0.1%, are also effective. 'I prefer to workbetween about 70 and 140 0., more particularly at about 120 C; At.

any rate, the presence of the auxiliary agents of the characterdescribed efiects that the reclaiming process is carried out at slowertemperature and more quickly, viz. within a few hours, i. e.

. under milder conditions than according to the hitherto knownprocesses. I

Examples for auxiliary agents of the characier-described are phenyihydrazine and its substitution products such as nitrophenyl hydrazine,

aryl hydrazines with inorganic salts. It is supposed that the monoarylhydrazines must be free from groups inducing solubility in water as suchgroups would prevent the interpenetration of the rubber to be reclaimedand of the auxiliary agents." The auxiliary agents of the characterdescribed can be incorporated within the vulcanizates in various ways,for instance, in a kneading machine, if desired with the addition ofagents exerting a certain softening effect and rubber and the saidauxiliary agents. As examples there may be mentioned: parafll'ne,co1ophonium or stearidacid, furthermore'- solvents such as benzene,toluene, xylene or mineral oils.

As examples for synthetic rubber-like materials which can be reclaimedfrom their vulcanizates there may be mentioned polymeric butadienes suchas polymeric butadiene-L3, or isoprene and co-polymerizates of suchbutadienes and other polymerizable compounds such as styrene. v

The following examples illustrate the present invention without,however, restricting it thereto, the parts being by weight:

Example 1 A 100 parts of a ground soft rubber vulcanizate are heated ina kneading machine with parts oi mineral oil and 5 parts of phenylhydrazine to C. for about 20 hours, free access of air. or oxygen beingallowed. The resulting product represents a soft and plastic materialwhich can a be easily worked up into vulcanizable mixtures and, uponvulcanization, yields products of good aging properties. In case theheating of the .soft rubber vulcanizate is performed under the sameconditionsbut without the addition of phenyl hydrazine, the resultingproduct still resembles vulcanized rubber rather than a unvulcanizedone.

aminophenyl hydrazine and toluyl hydrazine and the saltsthereof withorganic acids such as oleic acid, and finally, complex salts of the saidmono- 55 Example 2 15 parts of a ground vulcanizate of a syn theticrubber prepared by the emulsion polymerihours heating to C. thevulcanizate is strong-- 1y swollen and can be reused for vulcanization.

Example 3 v in case the synthetic rubber. of the character described inthe preceding example is replaced '75 parts of butadiene and 25 parts ofacrylic acid nitrile a somewhat longer heating (about 20 hours or more)is necessary to bring about a similar result.

, The above examples disclose the use of unsub stituted phenyl hydrazineit being to beimderstood that they are in no way limitative. Myexperiments have proved that phenyl hydrazine can be replaced with asimilar result by Bz-alkyl substitution products thereof such as toluylor xyloyl hydrazine and also by other substitution products such asnitroor aminophenyl hydrazine though the latter products do not appearto be as eilective as phenyl hydrazine itself.

I claim:

1. The reclaiming of vulcanized rubber scrap by the product of theemulsion polymerization of 15 the monoarylhydrazine is phenylhydrazine.

